After Some Missteps in Electronics, Sportswear Giant Courts App Makers for Its FuelBand Digital Bracelet

PORTLAND, Ore.—At a trendy loft here where DJs spin songs and assistants wheel in Red Bull energy drinks, Nike Inc. is embarking on an experiment that it says is increasingly crucial to its business: encouraging software developers to build applications for its FuelBand activity-monitoring device.

Nike is giving select developers terabytes of data from customers wearing the digital wristband. The company hopes the aggregate data—from the average duration of a run (35 minutes) to how energetic residents of certain cities...